maths question

a)
[(2p+2p+8)(2p)]/2 - {[(2p+8)/2]2p}/2
=4p^2+8p-p^2-4p
=3p^2+4p

b)
(4p^2+8p)(7/10)=3p^2+4p
28p^2+56p=30p^2+40p
2p^2-16p=0
p-8=0
p=8

c)
*****由於不能清楚閱圖，故未能寫出確實數值*****
i)
Draw a horizontal st. line which y = 5
The intersect point of the y = 5 and y = 3x^2+4x is the answer for ci
*****The negative value will be reject as length cannot be negative*****

ii)
Draw a horizontal st. line which y = 15
The intersect points of the y = 15 and y = 3x^2+4x is the answer for ci
*****Format : (-ve value)<p<(+ve value)

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